Such light-emitting panels can be used, inter alia, as backlight panels in liquid crystal display (LCD) devices, for example, TV sets, monitors, displays of computers, (portable) telephones, etc. Such light-emitting panels can also be used as luminaires for several lighting purposes, for example, shop lighting, with which objects can be seen through the panel illuminating the objects behind it. Furthermore, such light-emitting panels can be used on walls or ceilings of spaces or rooms which are evenly illuminated by means of these panels. The light source of the panel can be detachably connected to the light-entrance edge of the panel or may be an integral part of this edge.
A light-emitting panel of the type described above is disclosed in WO-A-2005/073622. This publication describes a rectangular transparent light-emitting panel having a front side and a rear side, in which cavities are present. These cavities are straight slits between the front side and the rear side, which slits are inclined with respect to the plane of the panel. One edge of the panel is provided with an array of light-emitting diodes (LEDs) in such a manner that the light radiation of the diodes is coupled into the panel. The light radiation which has been coupled in leaves the light-emitting panel by specular reflection against the side surfaces of the slits. By appropriate distribution of the inclined slits throughout the panel, the light is coupled out evenly through the entire front side of the panel.
Appropriate light-guiding materials for parts of the panel are transparent thermoplastics, in particular polymethyl methacrylate (PMMA), polycarbonate (PC), or polyvinyl butyral (PVB). Such materials can be shaped in an injection-molding process, an extrusion process, or a material-removing laser operation.
Due to the presence of cavities in the form of inclined slits, the light-emitting panel cannot have an uninterrupted front surface. Furthermore, it is a drawback that the cavities are in contact with the environment, so that their walls can be contaminated.